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(No Model.) 7 2 Sheets-Sheet 1. C. E; SGRIBNER.

Patented June 10,1884.

FOR (ELEARING OUT ANNUNCIATORS.

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(No Model.) 2 Sheets-Sheet 2.

C. E. SGRIBNER.

DERIVED GIRGUIT FOR CLEARING OUT ANNUNGIATORS.

No. 300,144. Patented June 10, 1884.

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CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE XVESTERN ELECTRIC COMPANY, OF SAME PLACE.

DE RIVED CIRCUIT FOR CLEARING-OUT ANNUNClATORS.

BPEL'IPICATION forming part of Letters Patent No. 300,144, dated June 10, 1884.

Application nan February 25, 1884. (No model.) I

To all whom it may concern.-

Be it kn own that I, CHARLES E. ScRrBNEn, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Derived Circuits for Clearing Out Annunciators of a Telephone-Exchange, (Case 73,) of which the followingisa full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to switch-board apparatus for tel ephone-exchanges.

In a prior application for Letters Patent, filed by me November 20, 1883, for improvement in operators apparatus for telephone switch-boards, I have shown and described apparatus for connecting together any two subscribers of a telephone-exchange, with mechanism adapted to connect the operators telephone-outfit into the circuit of the connected subscribers by the same act which disconnects the clearing-out drop from said circuit. By this arrangement the resistance of only one of the instruments is in the circuit of the subscribers connected lines at any time. This arrangement, while entirely practical, has some defects which I have sought to overcome by the present invention, hereinafter described. First, in connecting in one instrument and disconnecting the other, the circuit is for an instant broken, andin case the switch or connecting mechanism should for any reason fail to make contact the circuit would be left open; second, the circuit of the connected subscribers always contains the contact-points of the connecting mechanism, which are liable to become corroded, thereby adding to the resistance of the circuit.

My present invention consists in placing the clearingout drop permanently in circuit between the connecting-plugs, and providing mechanism whereby the operators outfit may be looped around the clearing-out drop, as hereinafter described and claimed.

In the accompanying drawings, Figure 1 is a diagram of circuits and apparatus embodying my invention. Fig. 2 is a diagram view of a single pair of connecting-plugs, and the circuit between them.

Like parts. are indicated by similar letters of reference in the different views.

A represents a switch-board, to which any suitable number of subscribers lines, a b, may be connected. These lines may be connected through suitable switches, a b, and calling-annunciators a to ground in the usual way. A connection between two subscribers is preferably made by means of the connecting-plugs c d, arranged in pairs, and provided with the usual conducting-cords, c d. Each pair of plugs has connected permanently in circuit therewith a clearingout annunciator, e, as shown in Fig. 2, and indicated by dotted lines f in Fig. 1. The annunciator e is connected on either side with the springs or levers g h of a loop-switch, B. This loop-switch B is adapted, when depressed, to bring the springs or levers g h into contact with the. contactpoints i k, and thus include the calling-keys Z m and the operators telephone-outfit n in circuit between the plugs c d. The loop-switch B may be made in any desired form. I preferably use a switch, as shown in Fig. 1, provided with a cam-lever, 0, adapted, when thrown up, to hold the bars of the switch in contact with the contact-points.

In making a connection between to subscribers, the operator inserts a pair of plugs in the switches to which the subscribers are connected. The subscribers are thus at once connected through a clearing-out drop. Vhen the loop-key B is depressed, a derived circuit is formed, and the current divides, a portion thereof going through the annunciator, and a portion through the telephone-outfit of the operator. It will be seen, now, that, although both instruments-the clearing-out drop and the operator s outfit-e-are in circuit at the same time, the resistance introduced into the subscribers circuit is less than when only one of the instruments is in circuit, on account of the derived circuit, which is formed by my system. The clearing-out annunciator being permanently in the circuit of the plugs, the circuit of the subscriber cannot be opened by failure of the points to make contact. An in crease of resistance in the derived circuit, caused by a partial failure of the loop-key to make contact, or by other causes, only results in sending more current through the other branch of the derived circuit, and does not therefore effect the talking-circuit.

Having thus described my invention, I claim- 1. The combination, with conducting-cords and terminal plugs for connecting two subscribers of a telephone-exchange, of a clearing-out annunciator connected permanently in circuit between said plugs, and switching apparatus whereby an operators telephone may be connected in a derived circuit around said clearing-out annunciator.

2. In a telephone-exchange, the combination, with telephone-lines emanating from a central office, and abranch line containing a signal device, and provided with means for temporarily connecting it at opposite ends with any two of said telephone-lines, of atelephone and switching apparatus whereby said 20 telephone may be connected into a derived circuit around said signal device.

3. The combination with the telephone-lines and a branch line provided with means for temporarily connecting it at opposite ends 25 with any two telephone-lines, of asignal device, and a telephone andswitch, said signal device being connected permanently with the circuit of said branch, and said switch being adapted to connect the said telephone in a derived circuit 30 around the said signal device.

In witness whereof I hereunto subscribe my name this 9th day of February, A. D. 1884.

CHARLES E. SCRIBNER.

Witnesses:

GEORGE P. BARTON, O. O. SHEPHERD. 

